Customer number is not the same as the business partner number

What causes this issue?

If you have set the <ZK>Same Numbers</> indicator for the business
partner and customer, then the numbers have to be the same.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Transfer a customer number that is the same as the business partner
number.
Check whether the correct settings have been made in Customizing in the
activity <DS:SIMG.V_TBD001>Assign Account Group to Grouping</>.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.